The Beatles - fixing a hole, 1967

"In his 2021 book The Lyrics, McCartney revealed that the most important influence for the song was a "little blue hole" he saw while under the influence of LSD. According to McCartney, "the most important influence here was not even the metaphysical idea of a hole… but this absolutely physical phenomenon – something that first appeared after I took acid. I still see it occasionally, and I know exactly what it is. I know exactly what size it is"."